First off: "Simple" does not mean boring. Stances are simple and easy to play and with a good variety of them, anything but boring.
Second: "Easy" does not mean simple. Every new player to D&D should not be required to first play a fighter, then play a rogue, then work their way up to the all-mighty caster. All classes should be "easy" to play, and once again, "easy" does not translate into "simple" or "boring."
The DDN fighter isn't just simple. It's boring. It's repetitive. It's uncreative.
First off: I find myself enthusiastically agreeing with the first sentence, then pulling a

at "given that, let's make things slightly more complicated".
Second: I've never tried to shoehorn a new player into any class, but I definitely don't think that all classes should be equally easy to play. The Wizard is 'great power that only the very
best can survive long enough to achieve', and the Fighter is the Working Man. Fighter is gritty, down-to-earth, and identifiable, Wizard is mysterious, rare, and the subject of awe.
In conclusion,
This only applies if you assume that the main focus of the game is combat, and even then it's rather shaky. Use your combat time creatively, and you'll find that where Rogues can do their 'Sneak Attack' well, Fighters are the class best suited for doing whatever you want.
The high attack bonus makes them ideal for combat maneuvers, throwing flaming oil, and using poisoned weapons. Their AC and hit points allow them to shrug off attacks that would leave any other character halfway to death.
You don't have a rogue in the party to pick this lock or disarm this trap? A war-hammer or heavy pick can total most locks, doors, and mechanical traps, and even some walls... especially if wielded by a character with Strength as their best stat.
The Fighter is unique in being the only class to have absolutely no unique abilities; it just does things that any class can do, but
better. If that's not what you're looking for, play a Paladin, Barbarian, or Ranger.